Small Cams and Falls

Hi Steph,
Great article! Thanks for the tips on gear. I am currently waiting out a Yukon winter before I put some more mileage on my cams. I’m still a bit of a trad newbie. Can I ask what is probably a silly question? Is there a size of cam that will no longer hold a fall and are designed to be for aid? I’m looking at this chart from Metolius that says cams fail at around 9kN. Does that mean cams that are rated lower than this are just for aid?
Duane

Hi Duane,
Brooke Sandahl is the VP and head of many things at Metolius, and a legendary Yosemite and Smith Rocks climber. I asked him for some clarification on your question, which I wanted to know too! I’m not sure if I’m glad or sad to see that I should continue to be totally gripped when climbing over those tiny pieces in sandstone Nonetheless,those littlest grey and purple master cams are a real sanity saver for me–when nothing else fits in the crack except tips of fingers, those give me the confidence to keep going. And when the cams get small, the more the better, for me, beyond the normal desert placement style of every body length: I like to have them just a few feet apart when they are tiny. And if I have to punch it past them, well, then I will not fall But I still like seeing the rope clipped to something down there….

But onto the real scoop. Here’s what Brooke had to say (thanks Brooke!!):

Cam ratings – Metolius Dec 12, 2011

Not a “silly” question at all. No question is “silly” when it involves life saving equipment.

As an analogy – think of wired stoppers. Look @ the smallest size of say our Astro Nut (# 1 = 2 kN /(450 lbf)…they are micro…tiny little wire for the body, wee little head for the actual stopper portion…doesn’t look like it could hold much…and it can’t (approx. 450 lbf). Look @ a # 10 Astro Nut – way beefier cable, way larger head ( # 10 = 10 kN / 2250 lbf)…so it’s pretty easy to see why one is rated much higher that another. It follows one should use the #1 Astro very judiciously…i.e. only for body weight applications only…it can’t be expected to hold a fall of any consequence. As an example (to give an idea of force) I put our engineer on the load cell and had him bounce test while standing in a aider (simulating a bounce test for an aid placement). He is a beefy Austrian, that weighs about 170lbs and just bounce testing with body weight (not even a rack or other gear on – he could get the load up to well over 400 lbs). In other words he is not that far from reaching the rated strength of the tiny #1 Astro Nut!

For example to give some idea what a kilo Newton ( kN) relates to (1kN = 225 lbf – so a 10 kN rated piece: (10 x 225 lbf = 2250 lbf ) –

The same analogy can be made with cams. As you get to the smaller sizes of cams all the parts must get smaller too. Units below about ¾ of an inch (range of the cam or crack size is what we are referring to here) in size must start using these smaller parts.

The Metolius #0, #00 have to use a smaller axle size just to be able to hold the cam lobes themselves. These smaller axles, although optimized through heat treating, still just don’t have enough size/ mass to withstand even moderate falls. The axle ends up bending (under a load/fall) and if it bends enough, the unit will pullout. These smaller units should be looked at as really only suitable for body weight applications or given enough time and judgment, accumulated over many years of experience…they may be used to hold falls…but the falls had better be small or you will pullout/destroy the unit.

When using micro gear, the order of the day is to place many backup pieces…so that if you blow out the top two, the third backup piece may hold your fall. Sometimes you will place up to 5 or 6 backup pieces above a crucial crux section (& know that you have some full strength pieces below those should they all fail!) Retreat is (almost) always an option! And for the beginning /intermediate climbers the wise one. Only seasoned experts have the judgment to gun for the anchors when running it out over micro gear. And even they must carefully weigh all the consequences and determine what if the piece(s) do pull, what will I hit, is it a clean fall, etc?

So units that are rated below 9kN aren’t necessarily aid pieces, but as pieces in the equipment chain get smaller and smaller…the consequences of their integrity should be heavily questioned. And at a certain point…the smallest pieces (micro gear) should really be thought of as able to hold body weight only (or referred to as aid pieces) – for safety’s sake!